Many types of pressure sensing systems for monitoring the pressure within the pneumatic tires of a vehicle have been proposed. In general, such systems, commonly known as tire pressure monitoring systems (TPMS), include tire pressure sensors located at each tire either as part of the valve stem or in other locations, such as in the tire wall or the tread.
Each of the sensors generates a pressure signal in the form of an electromagnetic (EM) signal. The electromagnetic signal is then transmitted by the sensor to a central receiver. The pressure signal generated corresponds to the pressure within the tire. When the tire pressure drops below a predetermined pressure, an indicator is used to signal the vehicle operator of the low pressure.
Properly inflated tires are important for achieving optimal fuel economy and vehicle handling. When the tire pressure monitoring system detects a low tire pressure situation, the vehicle operator is informed by the TPMS. Such problems are corrected either by replacing the low tire with a spare tire or filling the low tire to increase the pressure.
Once advised that the tire pressure is below the desired pressure, the vehicle operator takes steps to inflate the low tire to the proper pressure and, in so doing, either does not use a gauge at all, relying solely on the appearance of the tire, or uses a hand-held tire pressure gauge. The hand-held gauges are generally of the digital type, the analog dial type, or of the long, manual pencil type. While the quality of these gauges varies widely, it is very typical for a vehicle operator to rely on inexpensive and often inaccurate tire pressure gauge for the filling process. But cost alone is not a factor in determining accuracy of a gauge.
In any event almost every hand-held gauge regardless of price is less accurate than the tire pressure sensors provided as part of the TPMS. Accordingly, an obvious solution to the problem of inaccurate hand-held tire pressure gauges would be to have the TPMS sensors themselves transmit pressure values during the tire filling process. However, that solution creates several problems. An example of one such problem is the resulting reduced battery life in the TPMS sensor due to the increased number of transmissions during the lifetime of the sensor.
Accordingly, as in so many areas of vehicle technology, there is room in the art of tire pressure monitoring systems for vehicles for an alternative approach to tire pressure monitoring during manual inflation.